No value in SQLite

WorkDetailsTable.java

I have two tables, one is Info and another is WorkDetails.

Table Info: ID(PK), Name, Weather, Date, Status, TimeIn_Info, TimeOut_Info

Table WorkDetails: ID(PK),Project,WorkDescription,Per,TimeIn,TimeOut // 4 row

As you can see, I have 4 row in my WorkDetails. When I click button to insert them into SQLite, the 4 row and information in Table Info will be inserted. But what I want is, the row which contains value only will be inserted. If not, it will not be inserted.

Button btn1=(Button)findViewById(R.id.button2);
    btn1.setOnClickListener(new View.OnClickListener() {
        public void onClick(View arg0) {
            AlertDialog.Builder builder=new AlertDialog.Builder(WorkDetailsTable.this);
            builder.setTitle("Data Saved");
            builder.setMessage("Are you sure you want to save?");
            builder.setIcon(android.R.drawable.ic_dialog_alert);
            builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int ii) {
                    W1 = txtWork1.getText().toString();
                    W2 = txtWork2.getText().toString();
                    W3 = txtWork3.getText().toString();
                    W4 = txtWork4.getText().toString();
                    a1 = spinnerTra.getSelectedItem().toString();
                    a2 = spinnerTra2.getSelectedItem().toString();
                    a3 = spinnerTra3.getSelectedItem().toString();
                    a4 = spinnerTra4.getSelectedItem().toString();
                    P1 = per1.getText().toString();
                    P2 = per2.getText().toString();
                    P3 = per3.getText().toString();
                    P4 = per4.getText().toString();

                   if((W4.equals("null"))&&(P4.equals("null"))&&(h.equals(null))&&(i.equals("null"))) // check whether row 4 is null
                    {
                        checkRow3(W3, P3, f, g);// check row 3;
                    }

                    Toast.makeText(context, "Row 4 and 3 are empty", Toast.LENGTH_SHORT).show();

            builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int ii) {
                    dialog.dismiss();
                }
            });
            builder.show();


        }
    });
}

public void checkRow3(String a, String b, String c, String d)
{
    if((a.equals("null"))&&(b.equals("null"))&&(c.equals(null))&&(d.equals("null")))
    {
        return ;
    }
    else if(!d.equals("null"))
    {
        WD.insertWorkDetails(a3, a, b, c, d); // since row 3 not null, it will inserted into Table WorkDetails
       db.execSQL("INSERT into" + MyDatabaseHelper.TABLE_INFO + "(TimeOut_Info) values(?);", new String[]{d}); //insert d to Table Info column TableOut_Info
        Toast.makeText(this, "Done", Toast.LENGTH_SHORT).show();
        return;
    }

}

But the problem now is, it keeps on telling me that row 3 and row 4 are empty which suppose has value in row3. When I check data in SQLite, of course I get zero value in my SQLite. What's wrong with my code?